JPH0693976A - Diaphragm pump - Google Patents

Abstract

PURPOSE:To prevent deformation rupture of a diaphragm by preventing boosting of an oil-operated chamber when the feed pressure of a feed pump is reduced. CONSTITUTION:A space part in a pump body 1 is partitioned into an oil- operated chamber 9 and a pump chamber 10 by means of a diaphragm 7. A plunger 6 is reciprocatively inserted in a cylinder 4a, and a suction pipe 15 and a delivery pipe 18 for fluid are communicated to the pump chamber 10. A feed pump 17 is arranged in the suction pipe 15 and an oil supply passage 21 through which oil is supplied is communicated to the oil-operated chamber 9. An oil discharge passage 23 through which oil is dischargeable is communicated with the oil-operated chamber 9, and a leak valve 24 opened when the feed pressure of fluid generated by a feed pump 17 is reduced to a value lower than a given value is located in the oil discharge passage 23.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used as a fuel pump for a high-pressure fuel injection system of an engine, for example, and relates to a hydraulically driven diaphragm pump for reciprocally moving a diaphragm by hydraulic pressure to pump fluid (fuel). .

[0002]

2. Description of the Related Art For example, in a fuel injection system of a gasoline engine, increasing the pressure of fuel has been studied. As a fuel pump for this system, a hydraulically driven diaphragm pump capable of pumping fuel at high pressure is proposed. Note that, as a general diaphragm pump, for example, the actual Kaisho 5
There is a 5-88088 issue.

Conventionally, a feed pump is provided in the fluid suction pipe in order to increase the filling efficiency of the diaphragm pump, and an oil is supplied from outside the working chamber to the oil working chamber to prevent oil shortage due to oil leakage from the oil working chamber. There is one that connects the oil replenishment path for replenishing. An example of this will be described with reference to the sectional view of FIG. Note that the solid line in FIG. 9 indicates the bottom dead center state, and the chain double-dashed line indicates the top dead center state.

The pump body 1 has a box-shaped body 2 having an open side surface, a cylinder member 4 attached to the open end surface of the body 2, a metal diaphragm 7 and a backup plate 8 on the member 4. And a cover 3 attached in a state of sandwiching. The space formed by the body 2 and the cylinder member 4 is
The oil chamber 5 is filled with oil.

The diaphragm 7 is provided between the backup plate 8 and the cover 3, and the cover 3 and the cylinder member 4 are provided.
An oil working chamber 9 and a pump chamber 10 are defined by a space formed by
It is divided into and. The oil working chamber 9 is filled with oil, and the pump chamber 10 is filled with fuel as a fluid to be conveyed. A large number of oil passage holes 8a are penetrated through the backup plate 8. The surface of the backup plate 8 on the diaphragm contact side has a shape corresponding to the designed deformed shape of the diaphragm 7 at the bottom dead center.

The cylinder member 4 forms a wall portion of the oil working chamber 9, and a cylindrical cylinder 4a which projects toward the oil chamber is connected to the center of the wall portion. This cylinder 4
A plunger 6 is hermetically inserted in a so as to be reciprocally movable. The plunger 6 is reciprocated by a plunger drive mechanism (not shown) incorporated in the oil chamber 5. The plunger drive mechanism is composed of, for example, a cam that reciprocates the plunger 6 and a drive shaft that rotates this cam. The rotational force of the engine is used as a drive source that rotates the drive shaft, and Oil is used as lubricating oil.

A fuel intake pipe 15 and a fuel discharge pipe 18 communicating with the pump chamber 10 are connected to the cover 3. The suction pipe 15 includes a suction valve 13 which is a check valve, and is connected to a discharge port of an in-tank feed pump 17 in a fuel tank 16. This feed pump 1
7 has a discharge flow rate equal to or larger than the maximum discharge amount of the diaphragm pump and has a predetermined feed pressure. Discharge pipe 18
Is equipped with a discharge valve 14 which is a check valve,
It communicates with a delivery pipe equipped with an engine injector (not shown). The valve opening pressure of the discharge valve 14 is set to be equal to or higher than the feed pressure of the feed pump 17. The suction pipe 15 and the discharge pipe 18 form a fluid flow passage.

A cylinder 4a communicating with the oil working chamber 9
Inside, there is an oil chamber 20 provided outside the pump body.
An oil replenishment pipe 21 for replenishing the oil is communicated. The oil replenishment pipe 21 corresponds to an oil replenishment passage for replenishing the oil working chamber 9 with oil according to the present invention. The opening of the inner wall of the cylinder 4a of the oil replenishing pipe 21 (this is referred to as the tip opening) is opened and closed by the reciprocating plunger 6, and is opened at the bottom dead center of the plunger 6. The oil chamber 20 is open to the atmosphere.

Next, the operation of the diaphragm pump will be described. When the plunger 6 is reciprocated between the bottom dead center and the top dead center by the drive of the plunger drive mechanism, the diaphragm 7 is flexed in the reciprocating direction, and as a result, a pump action is performed as described below. . That is, when the plunger drive mechanism moves the plunger 6 from the bottom dead center to the right in FIG. 1 and enters the discharge stroke, first, the tip end opening of the oil refill pipe 21 is closed by the plunger 6. By increasing the pressure of the oil in the oil working chamber 9 as the plunger 6 moves,
The diaphragm 7 is displaced to the cover side (also referred to as the head side), and the fuel in the pump chamber 10 is pressurized. As a result, the pressure in the pump chamber 10 rises above the feed pressure of the feed pump 17 and the discharge valve 14 is opened, so that fuel is discharged from the pump chamber 10 to the discharge pipe 18. In addition,
During this discharge stroke, the oil in the oil working chamber 9 passes through the gap between the plunger 6 and the cylinder 4a and the oil chamber 5
It leaks though it is a small amount. After that, the plunger 6 is shown in FIG.
At, the top dead center indicated by the chain double-dashed line is reached.

When the plunger 6 moves from the top dead center to the left in FIG. 1 and shifts to the suction stroke, the pressure in the oil working chamber 9 decreases, and accordingly, the pressure in the pump chamber 10 lowers and discharges. The valve 14 is closed. When the pressure in the pump chamber 10 further decreases and becomes equal to or lower than the feed pressure of the feed pump 17, the suction valve 13 opens, so that the fuel pumped by the feed pump 17 is sucked into the pump chamber 10. Due to the pressure difference between the feed pressure of the feed pump 17 and the pressure in the oil working chamber, the diaphragm 7 moves to the back plate side. When the plunger 6 approaches the bottom dead center and the tip end opening of the oil replenishment pipe 21 is opened, the oil in the oil chamber 20 is replenished to the oil working chamber 9 through the oil replenishment pipe 21. It should be noted that this supplemental amount of oil is substantially equal to the amount of oil leaking from the oil working chamber 9 during the discharge process.

Further, when the plunger 6 is at the bottom dead center, the tip end opening of the oil replenishing pipe 21 is opened, so that the oil working chamber pressure becomes substantially equal to the atmospheric pressure, and the pump chamber pressure becomes equal to the feed pressure of the feed pump 17. Become. At this time, due to the pressure difference between the pump chamber pressure and the oil working chamber pressure, the diaphragm 7 is pressed against the backup plate 8 as shown by the solid line in FIG. Therefore, since the backup plate 8 receives the extra stress applied to the diaphragm 7 due to the feed pressure of the feed pump 17, the diaphragm 7 is prevented from being excessively deformed, and thus, is prevented from being broken by the deformation.

[0012]

During the operation of the diaphragm pump, the feed pressure may drop due to malfunction of the feed pump 17, failure, gas shortage, or the like. When the feed pressure is impaired in this way, the suction valve 1
3 and feed pump 17 and other losses cause pump room 10
The inside and the inside of the oil working chamber 9 tend to be negative pressure. Then, the oil in the oil working chamber 9 moves back and forth through the oil passage hole 8a of the backup plate 8 and the flow resistance is large, and the oil runs out before the diaphragm 7 reaches the backup plate 8. When the tip opening of the oil replenishment pipe 21 is opened in this state, the oil working chamber 9
Will be overfilled with oil. When the discharge stroke is started in this state, the diaphragm 7 is excessively deformed toward the head side (cover side) due to the pressure increase in the oil working chamber 9, causing deformation and destruction.

Therefore, the present invention has been made to solve the above-mentioned problems, and its purpose is to prevent deformation and destruction of the diaphragm by avoiding the pressure increase of the oil working chamber when the feed pressure of the feed pump is lowered. It is to provide a diaphragm pump that can be used.

[0014]

In the diaphragm pump of the present invention for solving the above problems, the space inside the pump body is divided into an oil working chamber filled with oil and a pump chamber filled with fluid by the diaphragm. A plunger is reciprocally inserted into a cylinder connected to the wall of the pump chamber, a fluid suction pipe and a discharge pipe are communicated with the pump chamber, and a feed pump for feeding the fluid to the suction pipe is provided. In a diaphragm pump in which an oil replenishment path for replenishing oil is connected to the oil working chamber,
An oil discharge passage capable of discharging oil is communicated with the oil working chamber, and a leak valve is provided in the oil discharge passage, which opens when the feed pressure of the fluid by the feed pump falls below a predetermined value. Is.

[0015]

When the feed pressure of the feed pump becomes lower than the predetermined value during the operation of the pump, the leak valve opens. Therefore, during the discharge stroke, the oil in the oil working chamber is discharged to the outside of the working chamber through the oil drain passage,
There is no pressure increase in the oil working chamber.

[0016]

【Example】

[First Embodiment] A first embodiment will be described with reference to the sectional view of FIG. Since this example is a modification of a part of the conventional example, the modified part will be described in detail, and the same or equivalent configuration as that of the conventional example will be designated by the same reference numeral in the drawings and will not be described. Omit it. Further, the same concept is applied to the following embodiments, and a duplicate description will be omitted. One end of an oil discharge pipe 23 is connected to the oil working chamber 9 of the diaphragm pump. The other end of the oil discharge pipe 23 is connected to the middle of the oil replenishment pipe 21.

The leak valve 2 is provided in the middle of the oil discharge pipe 23.
4 are provided. The valve chamber 25 of the leak valve 24 is
Two chambers 25 are provided by a diaphragm 26 with a valve body.
It is divided into a and 25b. The upstream (upstream) and downstream (downstream) pipes of the oil discharge pipe 23 are communicated with the chamber 25a (on the left side in the drawing). The other chamber 25
One end of the feed pressure introducing pipe 27 communicates with b. The other end of the feed pressure introducing pipe 27 is communicated with the pump chamber 10. The fuel in the chamber 25a and the oil in the chamber 25b are not mixed by the diaphragm 26 with the valve body.

In the oil side chamber 25a, the diaphragm 26 with a valve body is provided with a valve body 26a which opens and closes the pipeline of the oil discharge pipe 23 by its axial movement, and opens the valve body 26a. A spring 28 that biases in the direction is provided. This valve body 26a
In the normal operation of the diaphragm pump, the pump chamber pressure overcomes the spring force of the spring 28 and is held at the valve closed position, thereby closing the oil discharge pipe 23. A check valve 29 is provided upstream of the suction pipe 15.

When the feed pressure becomes lower than a predetermined value due to malfunction of the feed pump 17 or failure or gas shortage while the pump of the diaphragm pump is operating, the pressure in the pump chamber is reduced accordingly, so that the leak valve 24
The valve body 26a is opened by the spring force of the spring 28, so that the oil discharge pipe 23 is opened. As a result, during the discharge stroke, the oil working chamber 9
The excess oil is discharged to the oil replenishment pipe 21 through the oil discharge pipe 23, that is, leaks, so that the pressure in the oil working chamber 9 is not increased. Therefore, the excessive deformation of the diaphragm 7 due to the excessive replenishment of the oil in the oil working chamber 9 and the deformation and destruction thereof are prevented.

[Second Embodiment] A second embodiment will be described with reference to the sectional view of FIG. This example is a modification of the first embodiment. That is, in the first embodiment, the oil outside the pump body is replenished in the cylinder 4a, but in the present embodiment, the oil in the oil chamber 5 in the pump body is replenished in the cylinder 4a. Specifically, instead of the oil chamber 20 and the oil replenishing pipe 21 of the first embodiment, the cylinder 4a is provided with an oil replenishing hole 19 that communicates the inside and outside thereof. The oil replenishing hole 19 is opened and closed by the reciprocating plunger 6 in the same manner as the tip opening of the oil replenishing pipe 21. When the oil replenishment hole 19 is opened, the oil in the oil chamber 5 is removed from the oil working chamber 9
Will be replenished to. In this example, the oil replenishing hole 19 corresponds to the oil replenishing passage in the present invention. The downstream end of the oil discharge pipe 23 having the leak valve 24 is connected to the oil replenishment pipe 21.
Instead of this, it is communicated with the oil chamber 5.

In the diaphragm pump, when the feed pressure of the feed pump 17 becomes lower than a predetermined value, the leak valve 24 is opened, so that excess oil in the oil working chamber 9 passes through the oil discharge pipe 23 during the discharge stroke. Since it is discharged to the oil chamber 5, the oil working chamber 9
Is not boosted.

[Third Embodiment] A third embodiment will be described with reference to the sectional view of FIG. In this example, a part of the leak valve 24 in the first example is modified. That is, in the leak valve 24 of this example, the oil discharge pipe 23 is separated from the chamber 25a of the valve chamber 25, and the valve body 26 of the diaphragm 26 with a valve body is separated.
The tip of a is inserted into the L-shaped conduit of the oil discharge pipe 23 so as to be openable and closable. The tip end surface of the valve body 26a is directed downstream of the oil discharge pipe 23 so that the upstream pressure thereof does not act on the valve body 26a. The feed pressure introducing pipe 2 communicating with the chamber 25b of the leak valve 24
7 communicates with the intake pipe 15 instead of the pump chamber 10. According to this example, during normal operation of the diaphragm pump, it is possible to prevent the leak valve 24 from unnecessarily opening due to the pressure when the pressure in the oil working chamber 9 is increased.

[Embodiment 4] In Embodiment 4, as shown in the sectional view of FIG. 4, the leak valve 24 of Embodiment 3 is adopted in Embodiment 2.

[Fifth Embodiment] A fifth embodiment will be described with reference to a sectional view of FIG. This example corresponds to the first embodiment or the third embodiment.
The leak valve 24 in FIG. Specifically, a leak valve 31 formed of a solenoid valve is provided in the oil discharge pipe 23 in the middle thereof. The leak valve 31 is incorporated in an electric circuit including a battery (not shown) and is closed during normal operation of the diaphragm pump.
Further, the suction pipe 15 is provided with a pressure switch 32 for sensing the pressure inside the suction pipe 15, that is, the feed pressure of the feed pump 17. The pressure switch 32 outputs a detection signal when the pressure inside the suction pipe 15 drops below a predetermined value, and is incorporated in the electric circuit so that the leak valve 31 opens when the detection signal is output. ing.

When the feed pressure of the feed pump 17 becomes lower than a predetermined value during the operation of the diaphragm pump, the pressure switch 32 outputs a sensing signal to open the leak valve 31. Thereby, the first embodiment
Similarly to the above, during the discharge stroke, excess oil in the oil working chamber 9 is discharged to the oil replenishing pipe 21 through the oil discharge pipe 23, so that the pressure in the oil working chamber 9 is not increased.

[Sixth Embodiment] A sixth embodiment will be described with reference to a sectional view of FIG. In this embodiment, the leak valve 24 in the second or fourth embodiment is replaced with a leak valve 31 made of an electromagnetic valve as in the fifth embodiment. At this time, instead of the oil discharge pipe 23, the cylinder member 4 is provided with an oil discharge hole 30 that communicates the inside and outside of its wall, and a leak valve 31 is incorporated in this discharge hole 30. Along with this, the intake pipe 15 is provided with a pressure switch 32 for detecting an abnormal feed pressure in the leak valve 31.

[Seventh Embodiment] A seventh embodiment will be described with reference to a sectional view of FIG. In this embodiment, an electronic control unit (ECU) 33 is interposed in the signal transmission path between the pressure switch 32 and the leak valve 31 in the fifth embodiment. EC
When the U33 determines that the feed pressure is abnormal based on the sensing signal output from the pressure switch 32, the leak valve 3
The valve open signal is output to 1. The pressure switch 32 may be replaced with a pressure sensor.

[Embodiment 8] As shown in the sectional view of FIG. 8, Embodiment 8 is similar to Embodiment 7 in the middle of the signal transmission path between the pressure switch 32 and the leak valve 31 in Embodiment 6. A control unit (ECU) 33 is interposed.

[0029]

According to the present invention, since the oil in the oil working chamber is discharged when the feed pressure of the feed pump is lowered, the pressure rise in the oil working chamber can be avoided, and therefore the excess oil in the oil working chamber can be avoided. It is possible to prevent the diaphragm from being deformed and destroyed due to excessive replenishment.

[Brief description of drawings]

FIG. 1 is a sectional view showing a diaphragm pump according to a first embodiment.

FIG. 2 is a sectional view showing a diaphragm pump according to a second embodiment.

FIG. 3 is a sectional view showing a diaphragm pump according to a third embodiment.

FIG. 4 is a sectional view showing a diaphragm pump according to a fourth embodiment.

FIG. 5 is a sectional view showing a diaphragm pump according to a fifth embodiment.

FIG. 6 is a sectional view showing a diaphragm pump according to a sixth embodiment.

FIG. 7 is a cross-sectional view showing a diaphragm pump of Example 7.

FIG. 8 is a sectional view showing a diaphragm pump of an eighth embodiment.

FIG. 9 is a sectional view showing a conventional diaphragm pump.

[Explanation of symbols]

 1 Pump Body 4a Cylinder 6 Plunger 7 Diaphragm 9 Oil Working Chamber 10 Pump Chamber 15 Suction Pipe 17 Feed Pump 18 Discharge Pipe 21 Oil Replenishment Pipe (Oil Replenishment Path) 23 Oil Discharge Pipe (Oil Discharge Path) 24 Leak Valve

Claims (1)

[Claims] 1. A space inside a pump body is partitioned by a diaphragm into an oil working chamber filled with oil and a pump chamber filled with fluid, and a plunger is reciprocally inserted into a cylinder connected to a wall of the oil working chamber. A fluid suction pipe and a discharge pipe are communicated with the pump chamber, a feed pump for supplying the fluid is provided to the suction pipe, and an oil replenishing passage for replenishing oil is communicated with the oil working chamber. In the diaphragm pump, an oil discharge passage capable of discharging oil is communicated with the oil working chamber,
A diaphragm pump having an oil discharge passage provided with a leak valve that opens when the feed pressure of the fluid by the feed pump becomes a predetermined value or less.